Edmonds' Apple I Overview

Submitted by Tom Owad on May 22, 2004 - 5:06pm

 

 

                                                    Robert H. Edmonds
                                                    565 Bellevue Ave. #706
                                                    Oakland, CA 94610


                         APPLE-1 COMPUTER


     The Apple Computer is a complete microprocessor system, consisting
of an MOS Technology 6502 Microprocessor and support hardware, integral
video display electronics, keyboard connector, dynamic memory and refresh
hardware, and fully regulated DC power supplies.  It contains resident
system monitor software (in PROM), enabling the user, via the keyboard
and display, to write, examine, debug, and run programs efficiently.  It
is an educational tool for learning microprocessor programming and is an
aid in developing software.  It is the core of a first class hobbyist
computer system.

     The Apple Computer is sold fully assembled, tested, and burned in.  
The only external devices necessary for operation are: an ASCII encoded
keyboard, a video display monitor (or TV), and AC power sources of 8 to
10 volts and 28 volts.  The video display and keyboard eliminate the
usual need for a teletype, with its problems of noise and slow speed.  
They also eliminate the need for switches and lights, which, by comparison,
are painfully slow and awkward means for communicating with a computer.

     The integral video display section contains its own memory, leaving
all RAM for user programs.  Output formatin is 40 characters/line, 24 lines/
page, with auto scrolling.  Simple modification is usually all that is
necessary to adapt any TV for use as a display monitor.

     Almost any ASCII encoded keyboard with positive DATA outputs will
interface directly with the Apple system via a "DTP" connector.  If your
keyboard has negative logic DATA outputs (rare), you can install inverters
(7404) in the breadboard area.  Instructions for adaptation are provided
in the Apple-1 Operation Manual.  Since the system monitor accepts only
upper-case alpha (A-F, R--for hex coding and Run), it is desirable, though
not essential, to have a keyboard equipped with upper-case alpha lock
(usually in the electronics).  Although the video output displays only
upper-case alpha, both upper and lower case are encoded and are available
for hard copy output.

     The Hex Monitor is a PROM program in locations FF00 to FFFF (hex).  
It uses the keyboard and display to perform the front panel functions of
examining memory and entering and running programs.  The monitor program
is entered by hitting (RESET).  Commands are typed ona "line-at-a-time"
basis with editing.  Each line may consist of any number of commands (up
to 128 characters).  None are executed until (RETURN) is typed.  Hexadecimal
digits (0-9,A-F) are used for address and data values.  Additional command
symbols are: period (.), colon (: ), and R (for RUN).  Operation of the
monitor can be learned in just a few minutes time.

     The Apple-1 Operation Manual comes with each system purchased or can
be bought separately.  It includes the full Hex Monitor listing, detailed
Schematic Diagrams and provisions of the thirty day Warranty.

     All IC's are installed in sockets, thus simplifying repairs or
hardware troubleshooting.  The board has sockets for up to 8K bytes of
the 16 pin, 4K type RAM, and the system is fully expandable to 65K via
the edge connector.  The system uses dynamic memory (4K bytes supplied),
although static memory may also be used.  All refreshing of dynamic
memory, including all "off-board" expansion memory, is done automatically.  
The entire system timing, including the microprocessor clock and all
video signals, originates in a single crystal oscillator.  Furthermore,
the printed circuit board contains a "breadboard area", in which the user
can add additional "on-board" hardware (for example, extra PIA's, ACIA's,
EROM's and so on).  The board, as supplied, requires no more than 1.5 amps
DC from the +5V supply, while the regulator is capable of supplying 3 amps.  
The remaining 1.5 amps DC from the +5V supply is available  for user hard-
ware expansion (provided suitable transformers are employed).

      (Above data abstracted from Apple-1 Operation Manual.)

Bob Edmonds' Small Computers Center, PO Box 484, Actudillo Station, San
Landro, CA 94577  Temp. tel. (445) 357-5037                (5/17/76)

                           SPECIFICATIONS

MICROPROCESSOR:                       MOS TECHNOLOGY 6502

   Microprocessor Clock Frequency:    1.023 MHz

   Effective Cycle Frequency:         0.960 MHz

VIDEO OUTPUT:                         Composite positive video, 75 ohms,
                                       level adjustable between 0 and +5V pp.

   Line Rate:                         15734 Hz

   Frame Rate:                        60.05 Hz

   Format:                            40 char/line, 24 lines, with automatic
                                       scrolling

   Display Memory:                    Dynamic shift registers (1K x 7)

   Character Matrix:                  5 x 7

RAM MEMORY:                           16-pin, 4K Dynamic, type 4096 (2104)

   On-board RAM Capacity              8K bytes (4K supplied)

POWER SUPPLIES:                       +5 Volts @ 3 amps, +/-12 Volts @ 0.5
                                       amps, and -5 Volts @ 0.5 amps

   Input Power Requirements:          8 to 10 Volts AC (RMS) @ 3 amps,
                                      26 to 28 Volts AC (RMS) Center-Tapped,1A

Computer Type: 
Apple I
Manufacturer: 
Apple